1. Field of the Invention
This invention relates to techniques for switching boardmounted circuits, and more particularly to switching devices which access the board along an edge.
2. Discussion of Prior Art and Advantages of Present Invention
Heretofore most switches for printed circuits were located on the front panel because of space and accessibility requirements. Lead wires extend from the panel switches through the main frame to a connector which engaged edge terminals on the circuit board.
It is therefore an object of this invention to provide an edge-mounted switch for circuit boards which interfaces directly with conductors on the circuit board without intervening lead wires and connections.
It is a further object of this invention to provide a zero insertion force switching system which is mounted directly on the circuit board terminals.
Generally the prior art front panel switches were push-operated type requiring peripheral finger tip space, or toggle type requiring sufficient room to be activated by the side of the operators's finger. The size of the switch base, mounting structure, and lead terminals on the inside face of the front panel further prevented positioning these prior art panel switches in close proximity. Large switching matrices were located at the rear of the main frame or on special racks within the main frame.
It is therefore another object of this invention to provide a high-density, edge-switching system for circuit boards.
The prior art front panel switches were fixed in location because they were mounted in holes in the front panel. A major effort was required to reposition a single switch or reorganize a group of switches.
It is therefore a further object of this invention to provide a system of edge switches which can easily be repositioned and relabeled.
Some prior art panel switches were formed by an array of closely spaced slots for receiving small keys or U-shaped pins which engage the edge terminal of a printed circuit board. Traffic controllers employ such pin switches for defining the period of time permitted for a particular traffic phase. The slots in each row are associated with successive stages of a binary counter. Each slot represents a subperiod having twice the duration of the previous slot. The traffic phase period is determined by pinning the proper combination of subperiods. Under field conditions of adverse lighting and weather, the operators have difficulty in pin-pointing the proper slot. Sometimes the constant vibration from heavy truck traffic caused the pins to work loose. Further, the small pins were frequently lost in handling.
It is therefore an additional object of this invention to provide an edge-switching system with captive pins.
It is another object of this invention to provide an edge-switching system with position detents for locking the pin in the desired position.
It is still another object of this invention to provide an array of circuit board switches which provides sensory assurance that the desired switching action has been effected.